Explosive detonating device



United States Patent [72] Inventors Donald J. Lewis; Marina Del Rey; Frank H. Gardner, Huntington Beach, California [21] Appl. No. 666,365 [22] Filed Sept. 8, 1967 [45] Patented Sept. 15, 1970 [73] Assignee Space Ordnance Systems, Inc.

El Segundo, California a corporation of California [54] EXPLOSIVE DETONATING DEVICE 4 Claims, 2 Drawing Figs.

[52] US. Cl 102/70.2 [51] Int. Cl F42c 19/00 [50] Field ofSearch [02/27, 28, 70, 70.2

[56] References Cited UNITED STATES PATENTS 2,883,931 4/1959 Houck et al. l02/27X Primary Examiner Verlin R. Pendegrass Attorney-Warren T. Jessup ABSTRACT: The invention relates to an explosive detonating device adapted to be initiated by a sufficient amount of laser energy in the fon'n of coherent infra-red light applied by means of stranded fiber optics through a small shielded glass window to a first consolidated charge of relatively insensitive high explosive in a cup having a thin metallic bottom, the infra-red light igniting the charge which deflagrates at progressively increasing burning rates with accompanying high pressures and temperatures. The thin bottom then fractures and the metallic fragments are propelled at high velocities through a metal sleeve, which acts as a gun barrel for impacting the fragments upon the surface of a second consolidated charge of relatively insensitive high explosive charge at velocities sufficient to cause it to detonate, which in turn sets off the main charge.

FIG. 3

u! 1 an Patented Sept. 15, 1970 NVE DONALD wns BY FRANK GARDNER 7.

AT NEY.

W C u EXPLOSIVE DETONATING DEVICE The present invention relates to an explosive detonating device and more particularly to an explosive detonator having a small glass window and a plurality of consolidated high explosive charges contained in a metal housing for protection against electrical and mechanical hazards, the window serving to admit laser light for ignition of the first explosive charge which deflagrates and propels fragments of metal across an air gap, which fragments impact on a second consolidated high explosive charge causing it to detonate.

There has long been a need in the field of ordnance and explosives for a safe device to initiate large quantities of high explosives. Conventional detonators of the flash, stab, and electrical hotwire varieties usually contain a very sensitive primary explosive which can be actuated by flame, friction, heat, or mechanical drop and the presence of which, therefore, makes these items extremely hazardous to manufacture, store and use. In an effort toward greater safety, use has been made of the exploding bridgewire detonator which employs an extremely fine bridgewire encased in relatively insensitive high explosives, application of a high-voltage, short-duration impulse to the bridgewire serving to cause it to melt and ionize at shock wave velocities for initiation of the high explosives. Even the exploding bridgewire detonator, along with the electrical hotwire type, is subject to accidental and premature firing or dudding by uncontrolled electrostatic or radio frequency arcing and lightning.

It is, therefore, an object of the present invention to provide an explosive detonating device which has a high degree of safety and protection against mechanical and electrical hazards and is capable of manufacture, storage and use with relative safety.

Another object is the provision of an explosive detonating device which employs a firing train of high explosives that are no more sensitive than the main charge in an ordnance item.

A further object is to provide an explosive detonating device having a firing train of high explosives which is insensitive to normal light and is initiated by controlled admission of coherent infra-red light.

The exact nature of this invention as well as other objects, features and advantages thereof will be more readily appreciated from consideration of the following detailed description relating to the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a sectional view of one embodiment of an explosive detonating device in accordance with the present invention; and

FIG. 2 is a sectional view of another form of the explosive detonating device.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, wherein like reference characters designate like or corresponding parts, there is shown in FIG. 1 a detonator or explosive detonating device constructed in accordance with the present invention and designated generally by reference numeral 10. Device comprises a metallic casing or housing 12, having a bore 14 of such dimensions as to provide a thin bottom 16 and a relatively thick wall 18 to which a metal cap or cover member 20 is threaded as at 22. Cover 20 is formed with a flange or horizontally disposed portion 24 which may have a plurality of pairs of parallel sides for engagement by a wrench, or a pair of diametrically disposed holes or bores 26 adapted to receive a spanner, in order that the device 10 may be screwed into an ordnance item (not shown) by means of threads 28.

Disposed within cover 20, atop cup 12, is an annular holder 30 formed with a tapered aperture or perforation 32 and having a glass window 34 which is cast in aperture 32 and bonded to the walls thereof. Directly below window 34 is a cup-like formation comprised of a tubular metal sleeve 36 and a thin metallic disc or diaphragm 38, which may be integral, if

desired, instead of discrete. Housed within the cup-like arrangement defined by tube 36 and diaphragm 38 is a first charge in the form of a plurality of stacked high explosive pellets 40, 42 consolidated or compacted to high densities for reasons later appearing. Disc 38 rests upon a metal tube or tubular sleeve 44 which serves the double function of spacer and to define a gap 46 which may be filled with air or other gas or be a vacuum, partial or complete. Tube or sleeve 44 is disposed over a plurality of stacked high explosive pellets 48, 50 also consolidated or compacted and forming a second charge, the lowermost pellet 50 being in contact with bottom 16 of cup 12.

The explosive used in pellets 40, 42, 48, 50 is of the secondary class type, for example, pentaerythritol tetranitrate (also known as pentaerythrite tetranitrate) hereinafter referred to as PETN, cyclotrimethylenetrinitramine, hereinafter referred to as RDX, trinitrophenylmethylnitramine, hereinafter referred to as Tetryl, and hexanitrostyelane, hereinafter referred to as HNS.

As hereinbefore stated, each of the explosive charges is consolidated or compacted to high density. For example, in the case where PETN in powder form is used, an amount of PETN is subjected to about 10,000 pounds per square inch (psi) pressure to provide a pellet 50 having conventional detonator densities through which a detonator wave is readily propagated. Initiator pellet 48, however, is subjected to about 30,000 psi, as is each of pellets 42, cap pellet 40 receiving a dead press of about 60,000 psi. Thus, each of the pellets contains substantially the same amount or weight of explosive, but differs in volume because of the consolidation or compaction. The effect of the compaction is to render the higher density pellets less sensitive to detonation to the end that ignition of pellet 40 results in deflagration of the first explosive charge comprising pellets 40, 42, rather than detonation. It has been found in accordance with the present invention that the dead pressing of pellet 40 actually increases the sensitivity of the pellet to firing by the present method, while decreasing its sensitivity to conventional stimulations of the type heretofore used.

Controlled ignition of pellets 40, 42 is accomplished by the admission of 3V; joules energy of coherent infra-red light through window 34. The coherent infra-red light is conveyed from a laser source (not shown) by way of stranded fiber optics 52 protectively encasedin a metal sleeve 54 and plastic sheathing 56 bonded thereto. Sleeve 54 is received in a tubu lar extension 58, which is part of cover member 20, and held therein by a retainer sleeve 60, which is threadably connected to the extension, as at 62, and has a flange or shoulder portion 64 engaging a flange 66 on sleeve 54.

In the operation of the device 10, cover 20, with housing 12 and contents attached, is screwed firmly into the ordnance item after which fiber optics 52 are inserted and secured in place. When it is desired to detonate the ordnance item, a sufficient amount of energy, about 3% joules, of coherent infrared light is applied through the fiber optics 52 and glass window 34 to pellet 40, causing it to fuse and then burn. Because of the high densities, pellets 40 and 42 do not detonate but oxidize by deflagration with progressively increasing burning rates accompanied by a considerable build-up in temperature and pressures, window 34 and the tapered opening 32 in which it is supported being of sufficient dimensions to withstand the same. The flame and extremely high pressure front shears and fractures the metallic diaphragm 38 and propels the resulting metal fragments through the space gap 46 in sleeve or tube 44, which is in effect a gun barrel, for impacting the fragments on the second explosive charge (pellets 48, 50) at velocities great enough to decompose this charge at detonation rates, which causes the lower end of housing 12 to disintegrate and vaporize, resulting in setting off the main charge in the ordnance item.

Turning now to FIGIZ, there'is shown a detonator 10' in accordance with the present invention which is basically'the same as that in FIG. 1, but differs therefrom in certain aspects as will later appear. A cover member 20' has an upper position which is made up of parts or features 24', 26, 58, 60', 62, and 64, similar in purpose and function to their unprimed counterparts in FIG. 1, to which portion fiber optics 52 and accompanying parts 54, 56, and 66 are adapted to be connected as hereinbefore described. The lower portion of cover 20 is received in a cup-like holder 68, which has a bottom aperture 70 and shoulder 72 and is threadably connected to the cover as at 74. Cover 20' is also provided with a central bore 76 which houses a window holder 30 with a glass window 34' and receives the upper part of a sleeve-like member 36, the lower end of which is closed off by a metal disc or diaphragm 38'. Disc 38' rests upon a shoulder 78 formed in multibore cup member 12' which in turn is supported on shoulder 72 of holder 68, the lower portion of cup 12 extending through aperture 70 and having a thin bottom 16. The lower portion of cup 12' is filled with a secondary explosive S, compacted according to conventional detonator densities, atop of which is metal sleeve 44.

Within the lower part of sleeve 44' is a plug of secondary explosive 48', which is compacted to even higher density than explosive 50 and serves to keep the high pressure compaction of explosive 50 from relaxing, explosives 48 and 50 being akin in purpose and function to explosive pellets 48 and 50, respectively, of FIG. 1. Similarly, a secondary explosive 42, compacted to about the same density as explosive 48, fills the major portion of sleeve 36' and a secondary explosive 40, compacted to even greater density, fills the remainder of the sleeve, explosives 40 and 42 serving the same purpose as explosive pellets 40 and 42 of FIG. 1.

The space within sleeve 36 between the disc 38 and the top of explosive 48' defines a gap 46, the sleeve performing as a gun barrel and filled with air or gas or evacuated like sleeve 44 of FIG. 1.

The operation of device should be apparent from the foregoing description. However, briefly and in summary, coherent infra-red light is delivered through fiber optics 52 and window 34 for deflagrating the first charge of explosives 40, and 42", thus fragmenting diaphragm 38' and impelling the metal fragments down the jgunbarrel sleeve 44 for impaction on the second charge of explosives 42?,56' and detonation of the same.

It is understood, of course, that gaskets or the like for sealing or cushioning may be provided as desired or deemed necessary.

It is tobe noted that the explosive detonating device of this invention is loaded only with relatively insensitive high explosive charges, which are not any more sensitive to detonation than the explosive in the ordnance item the device is to detonate, and are protected by relatively heavy metal walls for protection against electrical and mechanical hazards. Not only is the device insensitive to normal light, but the small window is so located and shielded as to make it difficult to expose it to light and the device can only be actuated by controlled admission of coherent infra-red light through the window to effect a transition from deflagration to detonation. Tests indicate that the device can only be inadvertently fired or dudded by exposure to temperature environments in excess of 300F. and will always detonate when 3% joules of coherent infra-red light energy is applied to the ignition area of the detonator.

There has thus been provided a highly safe. detonating device which accomplishes the objects of the invention.

We claim:

1. An explosive detonating device comprising, in combination:

a housing defining a first container having an open top and a diaphragmatic bottom and containing a first explosive charge;

a glass window mounted in said housing adjacent said open top;

said first explosive charge consisting of a secondary class high explosive filling said first container and compacted to different densities with the greatest density being disposed adjacent said glass window; H

said housing defining a second container containing a second explosive charge spaced from said diaphragmatic bottom of said first container, and said housing defining a space gap between said diaphragmatic bottom and said second container;

said second explosive charge consisting of a secondary class high explosive filling said second container, the major portion of said last-mentioned explosive being compacted to detonation densities through which detonation is readily propagated; and

fiber optic means supported in said housing adjacent said window for passing coherent infra-red energy through said window from an external source to cause said first explosive charge to deflagrate and fragmentate said diaphragmatic bottom, so that said major portion of said second explosive charge is caused to detonate thereby causing the lower end of the housing to disintegrate and vaporize.

2. The explosive detonating device defined in claim 1, wherein: said first container comprises a tubular metallic sleeve and said diaphragmatic bottom comprises a thin metallic disc, and which includes a further metallic sleeve interposed between said first and second containers and defining said space gap.

3. The explosive detonating device defined in claim 1, wherein: said second explosive charge comprises a secondary class high explosive in the form of a plurality of pellets compacted to different densities and stacked in said second container, the pellets contiguous to the upper end of said second container constituting initiator pellets and being compacted to densities greater than the other pellets in said second container, such other pellets being compacted to detonator densities through which a detonation wave is readily propagated; and said first explosive charge comprising a secondary class high explosive in the form of a plurality of pellets compacted to different densities and stacked within said first container, with the pellets adjacent the top of said first container being compacted to greater densities than the pellets adjacent the bottom thereof, and with said last-mentioned pellets being compacted to substantially the same densities as those of said initiator pellets of said second explosive charge.

4. The explosive detonating device defined in claim 1, in which said housing includes a holder having a tapered aperture for supporting the aforesaid glass window, said glass window being cast in said aperture and bonded to the walls thereof, and in which said housing includes protective retaining means for mounting said fiber optic means with the ends thereof in contact with said glass window. 

